Shuttle control for looms



y 1965 H. sTuTz 3,181,573

SHUTTLE CONTROL FOR LOOMS Filed July 6, 1962 2 Sheets-Sheet 2 ATTQTLN SUnited States Patent C) 3,181,573 SHUTTLE CONTROL FOR LOOMS HansruediStutz, Zurich, Switzerland, assignor to A.G. Gebrucder Loepfe, Zurich,Switzerland Filed July 6, 1962, Ser. No. 207,868 Claims priority,application Switzerland, July 6, 1961, 7,887/ 61 4 Claims. (Cl. 139-341)This invention relates to shuttle control for looms and refers moreparticularly to an electromagnetic shuttle control device in looms,which operates without physical contact with the shuttle and whichactuates a releasing device to stop the loom when the movement of theshuttle becomes irregular.

Shuttle control devices in looms have the purpose of immediatelystopping the loom when movement of the shuttle becomes irregular.Improper movement of a shuttle can result from the following causes:

(a) The lay or lathe drive of the loom is worn out or has shifted.

(b) A part of the lay or lathe drive is broken.

The coupling is worn out and shifts or the driving motor is defectiveand runs, for example, only on two phases; in both cases the shuttleswould be insufficiently accelerated.

(d) The shed or parts thereof are not completely open and brake themovement of the shuttle.

(e) A single warp thread hangs through and brakes the movement of theshuttle.

In all these instances, if the shuttle control is ineffective, theshuttle would be located in the shed during the beating up of the reedand would tear a substantial number of warp threads or damage the reed.

In prior art mechanical shuttle control systems the shuttle uponreaching the shuttle box raises a resilient shuttle tongue and a pinconnected therewith. If due to the above-described circumstances theenergy of the shuttle is insuflicient to raise the pin, the battenduring the next beating up movement, will cause the pin to strike a stopmember, so that the batten is prevented from reaching its front endposition for the beating up of the reed. Since this control takes placeonly during the last phase of the shuttle movement, namely, when itpenetrates the box, and since, on the other hand, the loom must bestopped before the next beating up of the reed, there is extremelylittle time available for loom stoppage. Therefore, the operation islimited to a direct blow braking of the batten, and in the case of highspeeds this may easily result in breakage.

For these reasons it is desirable to provide means for detecting anirregularly moving shuttle at an earlier time, namely, at a time whenthe shuttle is still in the shed and not when it passes into the shuttlebox; such arrangement would make available more time for the stoppage ofthe loom, so that a normal brake could be used for that purpose. It hasbeen suggested to mount a coil in the path of the shuttle in which theshuttle induces a voltage impulse during each passage. If this voltageimpulse takes place later than at an instant which is set by a cammounted upon the batten shaft or the crankshaft, a stopping device isactuated. According to another suggestion, which is based on the samefundamental idea, the movement of the shuttle past a predeterminedlocation of its path is registered by optical means.

3,181,573 Patented May 4, 1965 ICC The main drawback of both of theseproposed solutions is based on the following consideration:

After the shuttle has been thrust, it moves in the loom as anindependent kinematic system and is no longer connected with the actualproducers of the weaving cycle, such as the crankshaft, batten shaftetc. If the movement of the shuttle past a predetermined section of itspath in relation to a time period determined by the position of the cambe taken as the criterion of the correct flight of the shuttle, thenthis is equal to the determining of the time period from the moment theshuttle is ejected by the beating up device to the moment when itreaches said predetermined location upon its path. However, since theshuttle moves during this time period from its end position to thelocation at which the release may be actuated, i.e., since it movesthrough a definitely determined portion of its flight path, theabove-mentioned determining of the time period means a roughdetermination of the speed of the shuttle. The speed is only approximatesince the shuttle, during its passage through the stretch beingdetermined, moves partly with an accelerated speed and partly with adecelerated speed, so that only an average speed can be determined inthis excessively long stretch. It can happen that, for example, theshuttle is excessively accelerated due to an excessive blow and afterbeing projected is excessively retarded due to insufiicient shedopening; these two errors may compensate each other, so that the shuttlewill pass through the designated location at the right moment and thecontrol will not be actuated, and yet the shuttle will not reach the boxdue to increased friction produced by the insufiiciently opened shed andthe corresponding loss in energy.

An object of the present invention is to eliminate the drawbacks ofprior art constructions.

Other objects will become apparent in the course of the followingspecification.

The present invention is characterized by the feature that instantaneousspeed of the shuttle is determined at one or more locations upon thepath of the shuttle and is compared with a set value. The scale for thisspeed comparison is supplied by an electronic time keeper which isindependent from the cycle of the loom.

Consequently, the present invention provides for determining theinstantaneous speed of the shuttle over a short passage at the locationof the releasing means, and not the determining of an average speed overa long path which includes the stretch during which the shuttle isaccelerated.

According to one embodiment of the present invention, two permanentmagnets are built into the shuttle, which release two voltage impulseswhen the shuttle flies past a coil mounted in the path of the lathe.

According to another embodiment of the present invention, only onepermanent magnet is built into the shuttle which induces a voltageimpulse in each of two coils mounted close to and behind one another inthe path of the lathe.

In both embodiments the time period between the two impulses whichfollow each other is compared with an impulse of constant duration. Assoon as the time between the impulses exceeds a permissible limit, i.e.,when the shuttle moves too slowly, a relay is actuated through anelectronic system, said relay being connected to the release magnet ofthe loom for stopping the loom.

, 3' A further feature of the present invention consists in that solelydiodes and/or transistors are used for the T time interval. fThislcaseis-- represented at the right hand electronic impulse receiving andtransforming purposes as non-linear or active switching elements, andthat in' these elements only the completely closed and the completelyconducting conditions are utilized. This arrangement takes intoconsideration the requirement for absolute lengthy time stability, sincethe electronic deviceoperates independently from the characteristiclines of the constructionelements' used therein; The requirementconcerning the highest possible lengthy time stability is ofutmostimportance for? shuttle control in looms, since it must be alwaystaken-in consideration that the loom is' a producing machinewhichisusually operated in threeshifts and which produces-from*200,000 to300,000 shuttle-inserted wefts in asingle day, whereby in large weavinges tablishmentsseveral; hundred machines are located in the881'11610011'1'. Therefore, unless the shuttle 7 control operates withthe greate'streliability, unpredictable: ditficulties will arise dueftothis exceptionally high-number" of inserted wefts: To: thesedifficulties-re sulting; from large amounts of w'efts, there are addedthe exceptionally high-shockandvibrationconditions in the sideofFIG.2,curves 21-26, where 26 is an output control impulse. V

The circuit elements 11-17 have the following functions: y

The clipping diode 12 short-circuit th positiv impulses of theinputsignal wave from'the coil 8 so that,

at pointl in FIG. 1, at each passage of the shuttle 7, two negativesignal impulses appear as indicated by curve 1 in FIG. 2'. 1

Circuit element 1 1- -is' a 'tiine pulse generator, or flipflop circuitwhich when triggered by the first of said negative signal impulsesoftlie curve 1: generates a fee tangular time impulse as represented bythecurves 2 and 22 in FIG; 2. This time" impulse has a predeterminedhave a time spacing equalfltothe duration of the recloomg; for example,during the ejection and th'e'braking i of the shuttle accelerationscan-occur duringnor'rnal operation-which amount to 110 times that oftheearth.

In accordance with-the presentinvention, the electronic impulseconverting device" operates with "mono stable'multivibrators orflip-flop devices and actualtime measuring takes place by me'ans' ofgate coim'ectionsl.

The invention will appear" more clearly from the rottangular timeimpulse, e.g. 20 milliseconds.

.The gate element13 together with the ditferentiating element 16" formsa time" discriminator circuit; The gateelement-13v has :a signalinput towhich" the signal impulsestcurve-l) from point 1" are" fed, and acontrol input-to, which the 'rectangular'tirne impulse (curvez)lOWingFdetailed. descrip'tionwhen taken in connection with theaccompanying drawings showing, by way of'example,preferredrembodinients"of tlie inventive, idea.

In-the drawings:

device of thepresent invention;

FIGURE l'shows' diagrammatically'ashuttle control FIGURE 2-" consists oftwelve diagrams representing voltages as a'functiQn -Oftime at differentlocationso'f the device: indicated" in FIG; 1, .during? normal opera=tiori ofthe'loom' and "alsowhen the shuttlemovesFat an. 7

improperly slow speed. FIGURE? :3-' illustrates"diagrammatically theshuttle and the control coilfintheir relation tothe -fabric.

FIGURE-4 is similar to FIG. 3 but illustr'ate'sadifferent constructionwherein two? controlcoi'ls are used, while the shuttle has one-magnet.

FIGURE 5' is sir'nilar'to FIG. 3 and 'illustrate'syt an otherconstruction wherein th'e shuttle-hastwo'magnets;

while two control coils are used." V

FIGURE 6" illustratesthe' shuttle" control device'of FIG. 1 ingre'aterdetail; particularly as fara'sth e 'various back in the shed containstwo permanent m gnets 9..

For explanation purposes; it is" assumed that" during thisl'tsiproCatOry movementithe' shuttle will"m6v' inthe directionindicated' by the arrow lfl'ipa'st a control 'coil 8. I A singlesignalw'ave rarer consisting} of a positive and a'negative signalimpulse'is"induced inthe' can 8 by;each'permanentmagnet'9? Thesignal impulses.are

fed to a control circuitry which 'consists of ith'e circuit elements11-17. The operation of the control circuitry is such that no outputcontrol impulse is generated when the two input signal waves fromthe-coil Sfhave a-time-y spacing-which is smaller than-a predeterminedtime ,in-- terval, e.g. 20- millisecondsl. This case is represented atthe left side of-FIG. 2, curves 16, Where 6 is the output controlsignal. On the other hand, an output =con-j trol impulseis-generatedwhenthe time spacing of said input signal waves is greaterthan said predetermined from point 2 is supplied. The gate element13'passes the first ofthe: inputfsign'al impulses-'to point' 5; However,the second of the inputsign'al impulses (curve ;1) is transmittedthroughgate 13?;on1y: if' it arrives? within the predetermined.time'int'ervahwhich" is defined .by the 'durationof the rectangular timeimpulse (curve-2)"; This case which indicates a proper shuttle flight isrepresented .bythe Cufv'e Z 5 in F163 2; In' case theshuttle is too 510Wand: the second input signal i'rnp'uls isj -late (curve 21), thisimpulse cannot pass the'gate"13 so that, at point 5' of'FIG. 1, acurverepresented by 25 FIGl'Zwillbe produced. a

I The circuitelements' 1'5"a'nd' 17 'together form'a si'g naltransforming? circuit which' in the case of two im' p'ulses'atp'oint' 5(see curve 5 in "FIG.'2)=,"delivers" no output signal as is representedby'curve' 6*in FIG; 2, but which in" the :faultycase'according to cuive'25 gen erates a'rect'an'gular' output'impuls'e'tsee curve 26), serv ingto stop' the loom' mechanism. Circuit' element 15 is a'controllablerectangular impulse generator or'flip -flop having a' first?input to whichthe sliarp time impulses (curve 3or23;'FIG.-2) are fed andasec' ond input to which the discriminatem'signal impulses (curve 5 or25; FIG; 2 fron'i'point' 5' are supplied; Thisflip-fldp generates, o'ntriggering fit with a single'neg'ative impulse, i.e. thefirst negativeimpulse in curve 3"or 23, a rectangular impulse of a" relatively longpredetermined duration, as represented by the curve 24w in FIG." 2! Theduration of this rectangular in'ip e" must be long enough, e.g., 300milliseconds;to" securethe actuation of the'Icwm StdPping echani mwhich" ec'curs ir'th'r appears no second negative" im ulse at the secondinput O' f flip-1101915" ('s'e e cll rve" zsrep'resentifi thefa-UItYCaTSE) However, when in the? casefof 'proper shuttle flight" a secondLnegative impulse (curve 5)" is" fed to th'e""seco'nd input of,"controllahle' flip flbp 15,- the latter impulse 7 causes resetting ofthisflip-flop't'o its n'oririalj'or lion-con ducting state,: 'softhat ,ashortened rectangular infpulse as represented bythe curve 4 isigeneratedatthe output, or point 4 of flip-flop 15L I I The endgate. element117hasa first-input to whicli the outputsignals of the: controllableflip-flop (curved on 24)' are fed, and a' second input to whichtherectangular time impulse (curves-2,- 22)- fromth'etimeim pulsegenerator 11 is supplied.

The end gate 17 is blocked by the negative rectangular time impulse sothat in case the impulse at point 4 is shorter than the rectangular timeimpulse as in the case of proper shuttle flight (see curve 4), no outputsignal occurs at point 6, FIG. 1. However, When as in the faulty casethe rectangular impulse (curve 24) lasts longer than the rectangulartime impulse from point 2, there will be produced a rectangular stopimpulse as represented by the curve 26 in FIG. 2, the end of whichimpulse is defined by the end of the rectangular output impulse of thecontrollable flip-flop 15, at point 4 (curve 24).

As shown in FIG. 6, the flip-flop 11 which is actuated by the firstsignal impulse from the coil 8, includes two transistors 40, 41 of theOC70 type interconnected by a condenser 51 of 0.5 microfarad andgrounded through a resistor 60 of 220 ohms. One of these transistors 40is connected with the point 1 through a diode 45 of the OA70 type. Atthe output terminal of the second transistor 41, namely, at the point 2,there Will appear a rectangular impulse of 20 milliseconds duration, asrepresented by the curve 2 in FIG. 2 This rectangular impulse istransmitted to a R-C, i.e. resistor-capacitor ele ment 14 which includesa condenser of 0.25 microfarad and which has a differentiating effect.Therefore, at the point 3 there will be produced a short negativeimpulse at the beginning and a short positive impulse at the end of the20 milliseconds rectangle (numeral 3 of FIG. 2). These short impulsesare transmitted to a second flip-flop the conducting time of whichamounts to approximately 300 milliseconds. The flip-flop 15 includes twotransistors of the OC70 and OC75 types which are interconnected by acondenser of 9 microfarads and a diode of the OA70 type; they are bothgrounded. The OC75 transistor is connected to a resistance of 220 ohmand to a battery of 12 volts. At the outlet of this flipflop 15, i.e. atthe point 4, will be thus produced a rectangular impulse having theduration of 300 milliseconds. The two impulses of the control coil 8 aretransmitted at the same time to a gate element 13 which is operated bymeans of the flip-flop 11 and which includes a diode of the OA70 type.This device permits the passage of impulses coming from the control coil8 only when the flip-flop 11 is in the conducting position. At theoutlet of this device again a differentiation takes place through theR-C (resistor-capacitor) element 16 having a condenser of 0.1microfarad; the impulses thus obtained are transmitted to the flip-flop15. The lastmentioned actuation serves the purpose of switching off theflip-flop 15, so that as soon as an impulse is received from the point5. The flip-flop 15 is brought back to its position of rest. The outletvoltage of the flip-flop 11 actuates at the same time a further gateelement 17 which operates upon the outgoing impulse of the flip-flop 15and which includes a diode of the OA70 type. Consequently, voltage ispresent at the point 6 only when the flip-flop 15 is still switched on,the flip-flop 11 being in its switched oif position. In that case therelay 19 is excited by the transistor 18 and will actuate by means ofits contact the magnet which stops the loom. The transistor 18 isgrounded through a resistance of 220 ohm. The relay 19 is connected to abattery of 48 volts.

Obviously, all these indications appearing in FIG. 6

' have been given by way of example only.

FIGURE 2 shows the curves of voltages as they appear at the points 1 to6 of the devices illustrated in FIGS. 1 and 6. At point 1 appear twonegative impulses transmitted from the control coil, which are spaced bya time interval of less than 20 milliseconds. Point 2 at at the outletof the flip-flop 11 has an impulse of a precise duration of 20milliseconds. Point 3 has a short positive impulse at the beginning ofthe 20 milliseconds rectangle and a negative impulse at the end thereofproduced by the element 14. Point 4 at the outlet of the flip-flop 15has a rectangular impulse which begins at the first coil impulse andwhich ends at the second co-il impulse, since the flip-flop 15 isbrought into its posi tion of rest by the second coil impulse. At point5 there are two short impulses which come from the coil impulses andwhich have passed through the gate device 13. Point 6 has always zerovoltage since the gate devide 17 stops the short impulse of point 4.

When the speed of the shuttle become smaller, there is a greaterdistance between the two impulses, as indicated, by way of example, at21. As before, in point 2 there will be produced a precisely 20milliseconds long rectangular impulse 22 which is supplied by theflipfiop 11.

Point 3 has a negative and a positive impulse 23 at the beginning and atthe end of the 20 milliseconds rectangle. Point 4 has an impulse 24which is 300 milliseconds long. Point 5 has only the first spool impulse25; the second spool impulse was suppressed by the gate device 13. Asthe result, the flip-flop 15 is not switched off any more and,therefore, at the point 4 there appears a 300 milliseconds rectangle 24.The gate device 17 permits the passage of this 300 milliseconds impulse24 as soon as the 20 milliseconds impulse 22 is terminated. Consequentlyat point 6 there is a voltage 26 which remains for 280 milliseconds andwhich actuates the relay 19 for 280 milliseconds through the transistor18. The switching off magnet is actuated by the contact 20 and the loomstops.

The shuttle control device of the present invention can be used in aloom in a number of different ways:

FIGURE 3 shows an embodiment wherein a control coil 30 is located in themiddle of the lay and wherein the shuttle 28 has two permanent magnets29. As soon as the shuttle 28 has passed with its second magnet thecontrol coil 30, the decision can be made as to whether its speed isadequate or not. Therefore, it is possible to brake the loom from thismoment on, if the speed of the shuttle is insufficient. It is obviouslyapparent that in this construction a substantially greater time isavailable for the braking of the loom than in prior art constructionswhich examine the presence of the shuttle at the end of the fabric inthe shuttle box.

According to the embodiment of FIGURE 4 the control is carried out byproviding two control coils 33 which operate parallel to the flip-flopconnections. In that case only one permanent magnet 32 is located in theshuttle 31, which induces an impulse first in one control coil and thenin the other control coil.

FIGURE 5 shows a further embodiment of the control device. In thisdevice there are two control coils 36 which again operate parallel tothe flip-flop connections. The shuttle 34 contains two permanent magnets35 and induces two impulses in each coil 36. Thus the flight of theshuttle is always measured at the beginning of the fabric, as well as atthe end of the fabric.

As already stated, the detailed switching connections are shown, by wayof example, in FIG. 6 in which the flipflops 11, 15 are provided withtransistors as switching elements, whereas the gate elements 13, 17 eachare formed by a diode and a resistor.

The whole circuitry is constructed so that the transistors have toprovide solely a definite minimum amplification factor. Above thisminimum the amplification factor may have any value without aifectingthe electrical circuit.

This results in a very securely functioning device, since the diodes andthe transistors at any time are either in a completely switched offposition or in a completely conducting position.

The following table indicates the various electrical components shown inFIG. 6, and their types or values unless already mentioned in thedescription to FIG. 1.

Table' Reference Component vane T e P t' 1 a v a i W is ensi n; '6 40...do 0970 As already stated, the d'e't aile'd switching" connectionswhichare shovvn,byway of example, in FIG.';6, coms' whieha're f med ymeans of erodes, vhilefth flip-flop" el fanned b transistors. Theswitching connections are s'o arranged that the transis' tofsreqfiire'the last possible strengthening; Above nii riimurnthe additionalstrength" can vary at will without affecting the function of the:electrical circuit; This. results' in'ai very securely functioningde'vi'ce, since the diodes arnavs and the transistors at any time areeither in a completely switched 01f position or in acompletelyconductingrposi i tion;

operates withv an egiceptiofially high safety; The basic criterion ofthe instantaneous speed vfor determining an improper flight of theshuttle better'suited'; fof solving this problem than was the case withlprior artconstructions; in particular, the braking of the shuttlebyw'arp threadsis properly t'ak'en'i'nto consideration and compens'a'tionby counter-acting processes, such as" ekeessive ac celeration' duringprojlec 1011 and'iexcessiv e' braking in the guide, is completelyeliminated Furthermore, the wiring is' very simple} since all parts ofthe control device are located closely to each' other in space; it isnot necessary to mount one part ofth device in thebatten; and the otherin'the shuttle drive, asis the case in prior art constructio'nsi a Thedevice operates substantially without inertia, due to (the elements"vusedin accordance with 'the present in- Th e shuttle controlldeviceg ofthe pres ent' ir ivntion' a W at la m d q t 1,111 a 10; havingi a lathea shuttle which reciting catcs along a predetermined path, and loomstopping means; a shuttle controlconiprising in combination with apermanent nagnet carried by the shuttle a pairot fiired coils located inthe" path of the lathe clbse to the path of th e shuttle and receivingma ne ic impulses f rqm'said permanent magnet while the shuttle movespast said Eons; electronic time eompariiig means connected with saidcoils and actuated by said'impulses, and meansoperatively connected withsaid electronic time-comparing means and said loom stopping: means andactuating said, looin stopping means when thetime difference determinedby "said electronic. time-comparing means deviates from apredeterminedtiine period. I I I, 7 t 2 In a1loom; having"a,lathe,ashuttle which recipro f cates alonga predetermiried; path, and loomstopping means; a shuttle control comprisihg," in combination with apair' of permanent magnets carried by the shuttle, a fitted coil locatedin the -pjath of the lathe close to the path of theshuttle and receivingmagnetic impulses from said permanentjrna'gnet's while the shuttlei'moves past said coil, electronic time-comparingmeans connected with saidcoil and actuated by said impulsleaand means operatively connected withsaidelectronictime-comparing means and said loom stopping means andactuating said loom stop: ping means when the time difference determinedby said electronic.time comparingrmeans deviates from a predeterminedtime period. p

3. In a loom havinga lathe, a shuttle which recipro ca'tes along apredetermined path, and loom stopping means; a shuttlecjontrolcomprising, in combination with a permanent magnet carried by theshuttle, a pair of fix'd eons located in the path of the lathe close tothepath 'of the shuttle and receiving magnetic impulses from' saidpermanent magnet while the shuttle moves pastsaid coils, a flip flopconnected with" said' coils'and actuated by one of salid impulses toproduce an impulse of predetermined duration, a gate element operativelyconnected with said loom'stop'ping' mean's, and means connected withsaid flip-flop and said gate element and actuatin'g sa'id gate elementto transmit an im'pulse to saidloom stopping means when a second impulsefrom said permanent magnet is irec eived by said flip-flop after thetermination of the impulse of predetermined durationl 4. In a' loomhaving a lathe, a shuttle which reciprocates along a predetermined path,and loom stopping means; a shuttle control comprising, in combinationwith a pair of permanent magnets carried by the shuttle, a'fixedt coillocated in, the path of the lathe close to the path of flip-flop andsaid gate element and actuating said gate element to transmit, animpulse to said loom stopping a means when a second impulse from saidpermanent magvention, namely, inductive emitters and electronicimpulse-varying means, thus further stressing the feature that a greateramount of -tiinieisavailable for'thebraking of theloom. The device ofthe resen invention, as com pared witnmeenahieardevices, has the:substantial advantage tha't'it has no mechafiic'allympvable parts'whichare subjetedto' wear a'ndf tear, so that for all practical purposes ithas an: irldefiniteilife' expectancy. I

It is apparen't that the examples described; above havebeen given solelyby way of illustration'aiid'notby way of limitation'and tha t th'e yare'siibje'ctito manyvariations and modifications the scope of thepresent inventiom All suchvariations and'modifications are to beineluded within the scope of the present invention.

nets is'received by'saidfiip-fiop after the termination of their'npulseof predetermined duration.

References Cited by the Examiner UNirED STATES PATENTS 2,586,335 2/52Howe et al 1'3 9-341 2,586,371 2/52 Moss et al. 139 341 2,756,782 7/56Applegate 139-341 2,781,794 2/57 Bordewieck et a1. 1'39 341 2,981,2964/61 Paul et a1 139"341 7 2,989,690 6/61 Cooke 324'-34 33,038,104 6/62Wessels' 32469 DONALD W. PARKER, Primary Examiner! RiUssELLc; MADER','MERVIN STEIN, Examiners.

Wolke 1 39 341

1. IN A LOOM HAVING A LATHE, A SHUTTLE WHICH RECIPROCATES ALONG APREDETERMINED PATH, AND LOOM STOPPING MEANS; A SHUTTLE CONTROLCOMPRISING, IN COMBINATION WITH A PERMANENT MAGNET CARRIED BY THESHUTTLE, A PAIR OF FIXED COILS LOCATED IN THE PATH OF THE LATHE CLOSE TOTHE PATH OF THE SHUTTLE AND RECEIVING MAGNETIC IMPULSES FROM SAIDPERMANENT MAGNET WHILE THE SHUTTLE MOVES PAST SAID COILS, ELECTRONICTIME-COMPARING MEANS CONNECTED WITH SAID COILS AND ACTUATED BY SAIDIMPULSES, AND MEANS OPERATIVELY CONNECTED WITH SAID ELECTRONICTIME-COMPARING MEANS AND SAID LOOM STOPPING MEANS AND ACTUATING SAIDLOOM STOPPING MEANS WHEN THE TIME DIFFERENCE DETERMINED BY SAIDELECTRONIC TIME-COMPARING MEANS DEVIATES FROM A PREDETERMINED PERIOD.